传染性支气管炎病毒S1和N基因遗传变异频率的分析

Genetic Variation Frequency of S1 and N Gene of Infectious Bronchitis Virus

旨在探讨中国北方地区传染性支气管炎病毒(IBV)的流行和分子变异,进而探讨IBV的遗传演变规律。利用生物信息学方法对IBV纤突蛋白(S1)和核蛋白(N)编码基因进行分析比较。结果显示:2012—2013年发生在山东、天津等北方地区的IBV流行株高度同源,其S1基因核苷酸(氨基酸)相似性为94.0%~100%(93.1%~100%),N基因为98.4%~99.1%(98.1%~99.8%),而与经典疫苗株H120相似性均较低,且至少在S1基因的3个高变区产生了较多的点突变、缺失和插入,且变异集中在第53—150和250—290位,以高变区HVR I居多,GM/13在62—65位缺失4个氨基酸。进一步的分析表明:IBV流行株S1基因与1998年在我国北方流行的A2株核苷酸相似性最高,为94.9%~97.2%,年核苷酸(nt)变异频率平均为2.4nt×10-3;而N基因则与LX4株相似性最高,为93.0%~93.5%,年变异频率平均为5.1nt×10-3。IBV流行株可能是A2-like和LX4-like毒株的重组,且N基因的变异频率明显高于S1基因。

This study was undertaken to investigate the prevalence and molecular variation of infectious bronchitis virus in the northern area of China.Thirteen infectious bronchitis viruses(IBV)strains obtained from commercial chickens in northern China between 2012 and 2013were isolated and identified by the sequencing of the entire S1 gene.The variants were distinguished by phylogenetic analysis and alignment in comparison with the vaccination-challenge tests that were performed using heterogeneous strains.The results showed that both the S1 and N gene of the prevailing IBV shared higher homologies.Furthermore,S1 gene shared nucleotide(amino acid)homology of 94.0%-100%(93.1%-100%),and N gene had nucleotide(amino acid)98.4%-99.1% homology(98.1%-99.8%),receptively.Compared with the classical vaccine strain,there were at least three hyper-variable regions were found in S1 gene,and point mutations,deletions and insertions of IBV strains were also occurred at the genomic level,which were concentrated in the 53-150,and 250-290.Four amino acids were found missing in GM/13 at 62-65.Further analy-sis showed that the IBV epidemic strains shared highest homology(94.9%-97.2%)with A2 strains and the nucleotide(nt)mutation frequency averaged 2.4nt×10-3/year in view of S1gene;while,the N gene was the LX4 strains of the homologous highest(93.0%-93.5%),the average annual variation in frequency 5.1nt×10-3/year.Those findings suggest that the recent IBV epidemic strains may be recombinant of A2 and LX4type strains,and N gene mutation frequency is greater than of the S1 gene.